1. Field of the Invention
The present invention relates to ink-jet recording heads used for ink-jet recording systems where recording liquid droplets are generated and relates to manufacturing methods of the ink-jet recording heads.
2. Brief Description of the Related Art
Ink-jet recording systems (i.e. ink-jet recording heads applied to liquid ejection systems) generally, are constituted of fine recording liquid ejection ports (hereafter referred as “orifice”), liquid paths and a plurality of liquid ejection energy generating elements constituted at portions of the liquid paths. In order to obtain images of high quality by employing such ink-jet recording heads, it is desirable to control an ejecting volume and a velocity of each liquid droplet ejected from the above-mentioned orifice, at the same level.
To attain such requirements, Japanese laid open patents from No. 4-10940 to No. 4-10942 disclose methods that driving signals are supplied to ink-ejection pressure generating elements (electro-thermal energy conversion elements) according to images to be recorded, to generate enough heat to raise an ink temperature immediately up to a higher temperature than nucleate boiling point of the ink so as to generate bubbles in the ink and so as to let ink eject by escaping force of the bubbles into the atmosphere.
For such purpose, an ink-jet recording head having a short distance between an electro-thermal energy conversion element and an orifice (hereinafter referred as “OH distance”) is desirable. In the above-mentioned methods, since the OH distance predominantly determines a volume of ejecting ink, it is necessary to keep the precise OH distance with good reproducibility.
As prior arts for manufacturing ink-jet recording heads, for example, Japanese laid open patents Nos. 57-208255 and 57-208256 which disclose methods that glass covers are bonded on nozzles consisting of ink paths fabricated by a patterning procedure of photosensitive resin applied on a base plate where the pressure generating elements are formed and a method disclosed by the Japanese laid open patent No. 61-154947 where ink flow path patterns are formed by soluble resin, and covered with epoxy resin etc. which is cured afterward, and is solved by a suitable solvent to remove the soluble resin after cutting the path patterns.
In above-mentioned manufacturing methods of the ink-jet recording heads, a growing direction of bubbles and an ejection direction of the ink are different, almost perpendicular to each other. And in these ink-jet recording heads, since a distance between a pressure generating element and an orifice is determined by cutting status of the base plate, a cutting accuracy is an important factor to control the above-mentioned distance. However, since the cutting is generally executed by mechanical means such as dicing saw etc., it is difficult to obtain recording heads with higher accuracy.
And as manufacturing methods of ink-jet recording heads characterized in that a growing direction of bubbles and an ejecting direction of ink are the same, Japanese Laid-Open Patent No. 58-8658, for example, discloses a method that a base plate and a dry film as an orifice-forming plate (hereinafter referred to as an “orifice plate”) are stuck together via another dry film with patterned liquid paths so as to form orifices by photolithography afterward.
However by any of the above-mentioned methods, it is difficult to manufacture an orifice plate with thin (e.g. less than 20 μm) and uniform thickness. Even if such an orifice plate is obtained, a connecting procedure of the base plate, where pressure generating elements are formed, with the orifice plate might be extremely difficult due to a fragility of the orifice plate.
In order to overcome such drawbacks, Japanese laid open patent No. 6-286149 suggests the following method. Namely, the method is comprised by the following procedures: a procedure to form ink paths patterned by a soluble resin on the base plate where ejection pressure generating elements are formed; a procedure to form a resin film layer for wall portion of ink paths on the soluble resin layer by solving a solid epoxy resin in a solvent at an ordinary temperature and by coating the epoxy resin solution on the soluble resin pattern; a procedure to form ink ejection ports on the resin film layer at corresponding portions to the ink ejection pressure generating elements; and a procedure to solve the soluble resin layer.
And an ink-repellant treatment is executed on the surfaces of ejection ports obtained by the above-mentioned procedure in order to prevent biased or no ink ejection due to stagnant ink that might generate on the surfaces of the ejection ports. The ink-repellant layers have been formed by a transfer method.
As disclosed in a Japanese laid open patent No. 5-124199, a photolithography method is proposed to form the ink-repellent layers on surfaces of ejection ports more accurately with no ink penetrations into the ejection ports.
Hereinafter a conventional example will be explained according to the above-mentioned technique by referring FIG. 9a to FIG. 9d. 
FIG. 9a to FIG. 9d show schematic sectional views of a ejection port. In these figures, numeric characters 31, 32, 33 and 34 represent a base plate, an orifice, an ink-repellent photosensitive resin film layer and a photo-mask, respectively.
The base plate 31 for ink-jet recording head having the ejection port 32 shown in FIG. 9a, is coated with photosensitive resin layer bearing a ink-repellent property as shown FIG. 9b so as to form the photosensitive resin film layer 33 is formed. Then after the photo-mask 34 which does not pass active energy rays, is placed over the photosensitive resin layer, a patterning exposure is executed by irradiating the active energy rays from directions shown by arrows in FIG. 9c. When the exposed pattern has been developed by the determined method, for example, by solving and removing non-polymerized (i.e. non-exposed portions) with solvents etc. and thus the ink-repellent photosensitive resin layer 33 has been obtained.
However, since images of high quality and of high resolution have been required, as seen such realized requirements in recent ink-jet printers, the size of every ejection port should be formed so fine that sometimes a some hundreds nano-meter discrepancy between corresponding portions of ejection ports of the liquid path forming material and of the ink-repellent layer, is caused by an insufficient patterning accuracy when patterning of the plate and of the layer are patterned on the same size. Because of the discrepancy, an ink-repellent property around the ejection ports is not so homogenous that the recording quality might be deteriorated.
In order to solve above-mentioned discrepancy, the liquid path forming resin as the first active energy setting material and ink-repellent surface treating resin as the second active energy setting material should be irradiated simultaneously.
However, in the case of the conventionally used spin coating method, there is a problem that since the liquid path forming resin as the first active energy setting material and ink-repellent surface treating resin as the second active energy setting material, are mutually solved, functions of these materials deteriorate, for example, sometimes the liquid path forming resin bears ink-repellent property, the ink-repellent resin decreases its ink-repellent capability etc., and distribution of the thickness of the layer becomes more fluctuated.